1. Technical Field
The present invention relates to a rotatable operation device for an endoscope.
2. Related Art
There are various forms of operation devices for operating a bendable portion of endoscopes. Many of such devices employ a mechanism which is configured such that a fixed shaft projects outward from an operating unit of the endoscope, and a cylindrical rotary shaft of an operation (rotatable) knob is fitted on the fixed shaft so that the cylindrical rotary shaft is rotatable about an axis thereof. Further, one end surface of the cylindrical rotary shaft is arranged to contact a stationary surface defined in the operating unit. An example of such a structure is disclosed in Japanese Patent Provisional Publication No. 2005-28018.
In endoscopes, the operating units have been formed to have a complete airtight structure (i.e., the internal space does not communicate with the outside) so that after-use cleaning, sterilization and the like can be performed completely. The operation knob has configured to have a certain internal space where a friction mechanism for stopping the operation knob at an arbitrary rotational position. Such an operation knob is also formed to be airtight.
In order to check the airtight configuration of the endoscope, a so-called a leak test is performed. The leak test is a test by injecting compressed air into the inside of an endoscope and then discharging it therefrom for inspecting existence of pinholes and the like, which may cause liquid leakage accidents.
FIGS. 6 to 9 illustrate processes of the leak test in sequence. As shown in FIG. 6, an operation unit of an endoscope is provided with a fixed shaft 92, which projects from an operating portion 91, and is formed to be airtight so that the internal space of the operating portion 91 does not communicate with the outside. Further, the operation unit is provided with an operation knob 94 having an internal space 93 and formed to be airtight so that the internal space 93 does not communicate with the outside. The operation unit has a cylindrical rotary shaft 95 which is rotatably fitted on the fixed shaft 92. One end surface of the cylindrical rotary shaft 95 contacts a fixing surface 96 defined inside the operating portion 91.
When the leak test is performed, as shown in FIG. 7, compressed air is injected through an open/close valve 97 communicating with the inside space of the operating portion 91. When the compressed air is injected through the open/close valve 97, the pressure inside the operating portion 91 increases. Then, the cylindrical rotary shaft 95 is moved outward along the axis, due to a play of its structure and due to a differential pressure between the pressure inside the operating portion 91 and the pressure in the internal space 93 of the operation knob 94 which initially had an atmospheric pressure.
The movement amount of the cylindrical rotary shaft 95, which moves from an initial position up to a position where the moving member comes into contact with a thrust stopper (not shown), is very small (e.g., approximately 0.1 to 0.2 mm). As the cylindrical rotary shaft 95 moves upward, a gap 98 is formed between the fixing surface 96 and the end surface of the cylindrical rotary shaft 95.
Consequently, as shown in FIG. 8, the compressed air is delivered from the space inside the operating portion 91 to the internal space 93 of the operation knob 94 through the gap 98 and a space formed an inter-fitting portion between the outer periphery of the fixed shaft 92 and the inner periphery of the cylindrical rotary shaft 95, whereby the pressure in the internal space 93 is increased. When the pressure in the internal space 93 reaches a predetermined value, the injection of the air is stopped, and it is examined whether leakage of the air occurs.
When the leak test is finished, as shown in FIG. 9, the open/close valve 97 is opened to reduce the pressure in the operating portion 91 to an atmospheric pressure. As the pressure is decreased, the cylindrical rotary shaft 95 is moved toward the operating portion 91 side (i.e., downward in FIG. 9) due to differential pressure between the pressure in the operating portion 91 and the pressure in the internal space 93 of the operation knob 94, which pressure has become higher than atmospheric pressure inside the operating portion 91. Accordingly, the end surface of the cylindrical rotary shaft 95 is press-contacted against the fixing surface 96, while frictional resistance and the like at a contact portion 100 between the operation knob 94 and its bearing member also become increased, whereby rotating operation of the operation knob 94 becomes heavy and its operability becomes low.